09/02/2016 | pH | 3 MINUTE READ

How to Monitor Aquarium Water pH and Other Water Quality Parameters

healthy aquarium water pH

The Importance of Aquarium Water Quality

Like all organisms, the fish and aquatic plants in your aquarium rely on highly specific environments in order to survive. These essential conditions vary from species to species and depend on the environment in which they evolved.

Aquarium Water pH

pH measures the acidity or alkalinity of water. A pH value of 7 is neutral, with lower numbers increasing in acidity and higher number increasing in alkalinity.

Many fish can thrive in a range of pH conditions, typically spanning 6.5 to 7.5 pH. However, some fish require specific pH conditions outside this range. It is a good idea to learn the ideal pH range for the fish you plan to raise in your aquarium. It is also important to ensure that all fish in the same tank have similar acceptable pH ranges.

The tap water that fills most aquariums generally has a pH between 6.5 and 7.5. However, pH can drift over time, so testing aquarium water regularly is important. Sometimes water may need to be treated to support healthy aquatic populations.

Why Monitoring Aquarium pH Matters

Most of the time, if left alone, pH levels will decrease over time due to additions of acids into to the water. Where could these acids be coming from? Here are a few common sources:

• Carbon dioxide in the air dissolving in the tank
• Tannins leeching into the water from plant matter
• Waste digesting bacteria acidifying the tank through the nitrogen cycle

Unfortunately, there are no visible indications that any change has taken place, so frequent monitoring is the only way to ensure that water remains healthy and inhabitable.

Tips for Testing Aquarium Water pH

The most accurate method for testing aquarium water pH is to use an electronic pH meter. You may be able to purchase a pH meter from a local pet supply store.

Adjusting Aquarium Water pH

You can lower aquarium water pH using commercially available peat or pH decreasers. Similarly, you can raise aquarium water pH using an alkaline buffer. Water hardness – or mineral content – may affect your ability to adjust aquarium water pH, as minerals can act as a buffer.

Large aquariums or commercial aquariums may benefit from using an aquarium monitoring system with an aquarium pH controller. The aquarium pH controller can be used to regulate addition of chemicals to aquarium water, which allows pH to be automatically controlled.

Other Important Aquarium Water Quality Parameters

Dissolved Oxygen

Dissolved oxygen is the form of oxygen available to fish in an aquarium. Oxygen is as fundamental to fish survival as it is for human beings. Undetected low oxygen levels could impair fish development and reproduction and even cause death.


ORP or oxidation-reduction potential is another testable parameter that could be useful in understanding the level of dissolved oxygen. Water that is contaminated with waste may have lower oxygen levels and a lower ORP. Measuring ORP may help to determine BOD or biological oxygen demand, which measures the amount of oxygen required to break down the organic waste matter generated.

Why Monitoring Dissolved Oxygen and ORP Matters

Oxygen is depleted by the fish that require it for respiration, but it is also depleted by plant life at night and by bacteria that help in the decay of organic matter. While oxygen can be added to the tank though photosynthesis and surface agitation, frequent monitoring is crucial to determine dissolved oxygen levels and ORP, so that these adjustments can be made as needed.

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Posted by Dominic O'Donnell on September 2, 2016

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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